The primary purpose of a safe and arm device is to prevent accidental functioning of a main charge of explosive (military or otherwise) prior to arming, and to allow an explosive train of smaller charges to detonate the main charge after arming. An explosive train is one form of an energy transfer mechanism. It typically begins with a very sensitive primary explosive that initiates detonation, continues through one or more less sensitive booster explosives that transmit and augment the detonation reaction, and finally terminates in detonation of a relatively large and insensitive main charge explosive to achieve the end result.
In an interrupted “out-of-line” explosive train, the sensitive primary explosive is physically separated from the booster explosive by an interrupter or barrier component of the safe and arm device. The barrier component, typically a slider or rotor, interrupts the explosive path and thus prevents detonation of the booster and main charge prior to arming. Arming occurs by moving the explosive train barrier component to align the explosive train's elements.
Conventional mechanical safe-arm devices (MSADs) employing interrupted explosive trains are relatively large & heavy, typically the size of a 12-ounce soda can and weighing several pounds. They are much too large for use in submunitions or micro “new tech” weapons. Furthermore, in the early 1990's, mechanically-based out-of-line technology gave way to the newer Electronic Safe-Arm Device (ESAD) technology which features an uninterrupted “in-line” explosive train containing no sensitive explosive components. However, ESADs, being exclusively electrical, contain much circuitry and many components which are physically large due to high-voltage ratings and/or derating requirements. Thus, existing safe-arm technology, whether out-of-line (MSAD) or in-line (ESAD), is not suitable for emerging small technology applications requiring safe and arm devices.
Micro-electromechanical systems (MEMS) have become known to a degree. The MEMS devices reported in the literature represents an achievement milestone in miniaturization and integration of electromechanical machines and devices. That technology provides, as example, a toothed gear that is smaller in size than a speck of dust, invisible to the eye. MEMS devices are sometimes fabricated by employing the photo-lithograph mask and etch techniques familiar to those in the semiconductor fabrication technology to form micro-miniature parts of silicon or other materials.